1. Field of the Invention
The present invention relates to a connector for holding a length of low-energy detonating cord (LEDC) adjacent a percussion-actuation end surface of a detonator, and to an assembly containing the connector for the field attachment of LEDC thereto and embedment in an explosive primer to be initiated.
2. Description of the Prior Art
Detonating cords are used in non-electric blasting systems to convey or conduct a detonation wave to an explosive charge in a borehole from a remote area. One type of detonating cord, known as a low-energy detonating cord (LEDC), has an explosive core loading of only about 0.1 to 2 grams per meter of cord length. Such a cord is characterized by low brisance and the production of little noise, and therefore is particularly suited for use as a trunkline in cases where noise has to be kept to a minimum, and as a downline for the bottom-hole priming of an explosive charge.
In blasting practice, an LEDC downline may be joined to an instantaneous or delay detonator attached to the blasting explosive charge, or to an explosive primer in said charge, in a borehole. Detonation of the LEDC actuates the detonator, which in turn initiates the blasting explosive charge or primer. The more sensitive the blasting explosive charge, the lower the explosive loading of the LEDC has to be to avoid detonation of the blasting charge before actuation of the detonator. With some blasting explosives, a core loading as low as about 0.5 gram per meter or less may be desired.
The most desirable cord-initiated detonators are those which do not require connection to the cord at the place of manufacture. A field-assembled detonator/cord system offers such advantages as safety and convenience during handling and storage, possible separate classification of the components for transportation, etc.
U.S. Pat. No. 3,709,149 describes a delay detonator adapted to be assembled in the field with a length of LEDC, the cord being disposed in a loop member outside a closed shell that contains an impact-sensitive ignition composition held, for example, in an empty primed rim-fired or center-fired rifle cartridge casing used as an end closure for the detonator. This detonator generally is positioned in a booster unit embedded in an explosive charge in a borehole.
U.S. Pat. No. 4,426,933, issued Jan. 24, 1984, to M. E. Yunan, describes an assembly in which a tubular metal primer shell, which supports a percussion-sensitive primer charge adjacent the inside surface of an integrally closed end, forms a closure for a detonator shell, and LEDC is arrayed adjacent the outside surface of the same integrally closed primer shell end in a manner such that a pair of segments of the LEDC are anchored in place in side-by-side relationship adjacent the outside surface. This cord array assures reliable ignition of a center- or rim-fired percussion primer by means of the side output of the LEDC even with explosive core loadings at the low end of the LEDC loading range. A preferred LEDC-affixing means is a sleeve which fits over the primer shell end of the detonator shell and has a projection in the form of a loop, bail, or half-hoop diametrically disposed beyond the integrally closed end of the primer shell. Most preferred is a generally M-shaped loop-like projection
U.S. Pat. No. 4,539,909 describes a detonator whose shell is closed with a hollow tubular plug containing a charge of sensitive explosive covered with a rupturable membrane. The plug has an extended portion in the form of a flat U-shaped container for receiving a U-bend of LEDC between spaced-apart faces.